KR20100137729A - White organic light emitting device - Google Patents

Abstract

PURPOSE: A white organic light emitting device is provided to improve the efficiency and lifetime of a device by using a mixed light emitting layer with two dopants doped on one host. CONSTITUTION: A white organic light emitting device comprises a first electrode(110) formed on a substrate(100), a second electrode(170), and a blue green mixed light emitting layer(140a) and a blue red mixed light emitting layer(140b). The blue-green mixed light emitting layer and the blue-red mixed light emitting layer are interposed between the first electrode and the second electrode. The blue-green mixed light emitting layer includes blue and green dopants doped on one host.

Description

White organic light emitting device

The present invention relates to an organic light emitting display device, and more particularly to a white organic light emitting display device.

OLEDs are attracting attention as ideal displays based on the advantages of ease of production, self-luminous, fast response speed, high brightness, wide viewing angle, low voltage driving, visible light emission in all spectrums and the feasibility of flexible displays. In particular, white organic light emitting diodes (WOLEDs) are widely recognized as the most important devices due to their wide application fields such as displays, backlights, and lighting, and are attracting attention as next generation devices to replace existing white light. The implementation method of the white organic light emitting device includes a single layer light emission method, a multi-layer light emission method, a color conversion method, a device stacking method, and the most widely used method of the light emitting occurs in several layers and the white by the vertical combination of each color It is a multi-layer light emission method. In the multilayer light emitting method, light emitting materials having light emission characteristics of red (R), green (G) and blue (B), which are three primary colors of light, are stacked (three wavelength white organic light emitting diodes), or light emitting materials having complementary colors are stacked. (Two-wavelength white organic electroluminescent device), and in lighting, three-wavelength electroluminescent device is used more than this wavelength to increase color rendering index (CRI) and color tube temperature (CCT). However, a device having a multi-layered structure composed of a material emitting red, blue, and green light emitting layers is not only easy to form a multilayer film, but also varies in color depending on voltage, and its lifespan is very short due to poor stability of the device itself. Has its drawbacks.

The technical problem to be solved by the present invention is to provide a white organic light emitting device having improved efficiency and life characteristics.

One aspect of the present invention to achieve the above technical problem provides a white organic light emitting device. The device may include a first electrode, a second electrode, and a light emitting layer interposed between the first electrode and the second electrode and including a blue-green mixed light emitting layer and a blue-red mixed light emitting layer.

The blue-green mixed light emitting layer includes blue and green dopants doped in one host, and the doping concentration of each dopant may be 0.1 wt% to 50 wt%.

The blue-red mixed light emitting layer includes one host and a doped blue and red dopant, and the doping concentration of each dopant may be 0.1 wt% to 50 wt%.

The white organic light emitting diode is interposed between the first electrode and the light emitting layer, and is interposed between the hole injection layer on the first electrode and the hole transport layer on the hole injection layer, and between the second electrode and the light emitting layer. And an electron transport layer on the light emitting layer and an electron injection layer on the electron transport layer.

At least one of the first electrode and the second electrode may be an electrode having a transmittance of 50% or more.

As described above, according to the present invention, using a mixed light emitting layer doped with two dopants in one host, the singlet generated in the host is dispersed into two dopants to emit light of each dopant, and the interface of the light emitting layer By reducing the number and reducing the probability of generation of exciplexes, the lifetime and efficiency of the device can be improved.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Like numbers refer to like elements throughout.

1 is a cross-sectional view showing a white organic light emitting display device according to an embodiment of the present invention.

Referring to FIG. 1, the first electrode 110 is formed on the substrate 100. The first electrode 110 may be formed as a transparent electrode or a reflective electrode. When the first electrode 110 is a transparent electrode, it may be formed using indium tin oxide (ITO) or indium zinc oxide (IZO), and if the first electrode 110 is a reflective electrode, Ag, Al, Ni may be used. , Pt, Pd or alloys thereof. As a result, the first electrode 110 may be formed as an anode.

The hole injection layer 120 and the hole transport layer 130 may be sequentially formed on the first electrode 110. The hole injection layer 120 is a layer that facilitates the injection of holes into the light emitting layer 140 formed in the process described later, using a material such as CuPc, TNATA, TCTA, TDAPB, TDATA, DNTPD, PANI or PEDOT Can be formed. In addition, the hole transport layer 130 is a layer that facilitates the transport of holes to the light emitting layer 140 formed in the process described later is formed using a material such as α-NPB, TPD, s-TAD, MTADAT or PVK can do. In some cases, at least one of the hole injection layer 120 and the hole transport layer 130 may be omitted.

The emission layer 140 is formed on the hole transport layer 130. The light emitting layer 140 may include a blue-green mixed light emitting layer 140a and a blue-red mixed light emitting layer 140b. The blue-green mixed light emitting layer 140a includes blue and green dopants doped in one host, and the doping concentration of each dopant may be 0.1 wt% to 50 wt%. The blue-red mixed light emitting layer 140b includes blue and red dopants doped in one host, and the doping concentration of each dopant may be 0.1 wt% to 50 wt%. In the case of using only one material as a light emitting material, the maximum light emission wavelength is shifted to long wavelength due to intermolecular interactions, and mound peaks are generated at long wavelengths, resulting in poor color purity and low efficiency. Therefore, light emission efficiency is increased by increasing color purity and energy transfer. In order to achieve this, it is preferable to use a host / dopant system. In particular, in the present invention, the singlet generated in the host is dispersed into two dopants by using a mixed light emitting layer doped with two dopants in one host to emit light of each dopant, and the number of interfaces of the light emitting layer is reduced. By doing so, the life and efficiency of the device can be improved. In addition, although the mechanism is not yet clearly understood, when the mixed light emitting layer is used, the dopant, the dopant, and the dopant are reduced by reducing the doping concentration as compared to the case where the green, red, and blue light emitting layers are individually doped to each host. It is possible to increase the lifetime of the device by reducing the probability of generating exciplexes between the host and the host, and also minimize the phenomenon that the original light of the dopant is not emitted by the light emitted from the exciplex. It seems to contribute to the improvement of the efficiency of the device. By using a blue dopant in common in each mixed light emitting layer, it is possible to reinforce the efficiency of a blue device having low efficiency compared to red and green. The structure of the light emitting layer 140 may be a blue-red mixed light emitting layer 140b on the blue-green mixed light emitting layer 140a, and vice versa.

The electron transport layer 150 and the electron injection layer 160 may be sequentially formed on the emission layer 140. The electron transport layer 150 is a layer that facilitates the transport of electrons to the light emitting layer 140 may be formed using a material such as PBD, TAZ, spiro-PBD, Alq3, BAlq or SAlq. . The electron injection layer 160 is a layer that facilitates the injection of electrons into the light emitting layer 140 may be formed using, for example, Alq 3, LiF, gallium mixture (Ga complex) or PBD. In some cases, at least one of the electron transport layer 150 and the electron injection layer 160 may be omitted.

The second electrode 170 may be formed on the electron injection layer 160. The second electrode 170 may be formed using Li, Mg, Al, Ca, Ag, Al-Li, Mg-In, or Mg-Ag. In the case of a transparent electrode, the second electrode 170 may transmit light. It is formed thin, and in the case of a reflective electrode is formed thick. As a result, the second electrode 170 may be formed as a cathode. At least one of the first electrode 110 and the second electrode 180 is formed of a transparent electrode that can transmit light.

Alternatively, the first electrode 110 may be formed of a cathode, and the second electrode 170 may be formed of an anode. In this case, the organic light emitting display device includes the first electrode 110, the electron injection layer 160, the electron transport layer 150, the light emitting layer 140, and the hole transport layer 130 on the substrate 100. The hole injection layer 120 and the second electrode 170 may be formed to have a stacked structure in this order.

Hereinafter, preferred examples are provided to aid the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited to the following experimental examples.

<Production Example>

ITO was formed as a first electrode on the substrate, and DNTPD was formed to a thickness of 600 kPa as the hole injection layer on the ITO, and then NPB was formed to a thickness of 200 kPa as the hole transport layer thereon. Doping 1% by weight of BCzVBI (blue dopant) and 0.2% by weight of GDI-4501 (Grasel) (green dopant) to the ADN (host) to form a blue-green mixed light emitting layer with a thickness of 50 Å on the hole transport layer. Formed. The blue-green mixed light emitting layer was mixed with a thickness of 100 μs on the blue-green mixed light emitting layer by performing the same method as the method of forming the blue-green mixed light emitting layer, except that 0.2 wt% DCJTB was used as the red dopant instead of the green dopant. A light emitting layer was formed. Next, Alq3 was formed on the blue-red mixed light emitting layer to have a thickness of 250 mW as the electron transport layer, and then LIF was formed to a thickness of 10 mW as the electron injection layer. Finally, Mg-Ag alloy (Mg: Ag = 9: 1) was formed to a thickness of 150 으로 as a second electrode having a transparent property on the electron injection layer.

Comparative Example

ITO was formed as a first electrode on the substrate, and DNTPD was formed to a thickness of 600 kPa as the hole injection layer on the ITO, and then NPB was formed to a thickness of 200 kPa as the hole transport layer thereon. ADI (host) was doped with 2% by weight of GDI-4501 (Grasel) (green dopant) to form a green light emitting layer having a thickness of 20 kPa on the hole transport layer. ADN (host) was then doped with 2% by weight of DCJTB (red dopant) to form a red light emitting layer with a thickness of 50 kV on the green light emitting layer, and 2% by weight of BCzVBI (blue dopant) was added to the AND (host). Doped to form a blue light emitting layer in order of 300 Å thickness on the red light emitting layer. Next, Alq3 was formed to a thickness of 250 kPa on the blue light emitting layer as an electron transport layer, and then LIF was formed to a thickness of 10 kPa on the electron injection layer. Finally, Mg-Ag alloy (Mg: Ag = 9: 1) was formed to a thickness of 150 으로 as a second electrode having a transparent property on the electron injection layer.

The characteristics of the white organic light emitting diodes manufactured according to the Preparation Examples and Comparative Examples are shown in Table 1 below.

TABLE 1

Voltage (V) Luminance (cd / m ² ) Efficiency (cd / A) Color coordinates (CIE) Life (T ₈₀ ) Production Example 6 4000 10.5 0.35, 0.33 1400hr Comparative example 6 3200 4.75 0.33, 0.30 200hr Life time (T ₈₀ ): The time when the luminance of each device is reduced to 80% of the initial value (5000cd / m ² ) when the same current density (DC) is applied.

2 is a graph showing the efficiency characteristics of the white organic light emitting diodes manufactured according to the Preparation Example and the Comparative Example.

3 is a graph showing the lifespan characteristics of the white organic light emitting diodes manufactured according to the preparation example and the comparative example.

Referring to Table 1 and FIGS. 2 and 3, in the white organic light emitting display device according to the present invention, the (x, y) coordinates of the CIE color coordinates represent the color coordinates of the white light source. It can be seen that the life characteristics.

Therefore, a blue and green dopant is doped in one host and a blue and red dopant is doped in one host than a device including a light emitting layer in which green, red and blue dopants are doped in each host and stacked in a multilayer structure. It can be seen that the light emitting device according to the present invention including the doped mixed light emitting layer is excellent in terms of efficiency and lifespan.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes by those skilled in the art within the spirit and scope of the present invention. You can change it.

1 is a cross-sectional view showing a white organic light emitting display device according to an embodiment of the present invention.

2 is a graph showing efficiency characteristics of white organic light emitting diodes manufactured according to Preparation Examples and Comparative Examples.

3 is a graph showing the lifespan characteristics of the white organic light emitting diodes manufactured according to Preparation Examples and Comparative Examples.

Claims (5)

A first electrode; Second electrode; And And a light emitting layer interposed between the first electrode and the second electrode and including a blue-green mixed light emitting layer and a blue-red mixed light emitting layer. The method of claim 1, The blue-green mixed light emitting layer includes a blue and green dopant doped in one host, and each dopant has a doping concentration of 0.1 wt% to 50 wt%. The method of claim 1, The blue-red mixed light emitting layer includes one host and a doped blue and red dopant, and each dopant has a doping concentration of 0.1 wt% to 50 wt%. The method of claim 1, A hole injection layer interposed between the first electrode and the light emitting layer and positioned on the first electrode and on the hole injection layer; And The white organic light emitting diode interposed between the second electrode and the light emitting layer, and further comprising an electron transport layer located on the light emitting layer and the electron injection layer on the electron transport layer. The method of claim 1, At least one of the first electrode and the second electrode is a white organic electroluminescent device is an electrode having a transmittance of 50% or more.

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